Hurricane’s Deep-Ocean Roar Sounds Its Strength

An MIT engineer has a radical idea for determining just how strong a hurricane is: Analyze the sound of its roar, recorded by hydrophones 800 meters under the surface, to calculate the speed of its winds.

The new system could unfortunately reduce the number of $100 million hurricane-monitoring planes and their quiver of nature-measuring gadgets. The system could have its largest impact in southeast Asia where the expense of cyclone monitoring is harder for countries’ governments to bear.

In a paper accepted by Geophysical Research Letters, Nicholas Makris, director of MIT’s Laboratory for Undersea Remote Sensing, describes how new analysis of Hurricane Gert’s fortuitous 1999 passage over a hydrophone provides the first real-world proof that his theory could work under real conditions.

That "gift from God" provided Makris with his first field recording of a hurricane’s oceanic acoustic signature. Comparing his theoretical model with actual sound and wind data measured by an aircraft allowed Makris to calculate the acoustic signatures of various wind speeds. In effect, dropping hydrophones in front of advancing hurricanes could create a low-cost hurricane measurement system.

"The theoretical models were saying this should work and that there should be some kind of relationship between the sound and wind," Makris said. "That is exactly what we saw. It worked out beautifully."

More whimsically, but in line with our fascination with underwater microphones, we’ve obtained the unedited sound of a hurricane’s roar straight from the dark depths of the Mid-Atlantic Ridge. You can listen to it at the right, but beware of cranking it too loud with a good subwoofer.

"Personally, I find the sounds to be very scary; longer listening actually makes me seasick," Makris said. "We often work in very bad conditions at sea,
30 to 40 knot winds, but this is 100 knots driving the seas, probably wave heights of 60 to 120 feet."

The sound is caused by the crashing of waves and general turbulence at the surface — the same types of phenomena that would toss a boat around in a storm. But by the time those waves propagate into the depths, all that sturm und drang has faded into the barely audible, very low frequency sound you hear.

Right now, Makris is working with Mexican authorities on a tiny island that’s often buffeted by storms to try to capture the underwater sound of another hurricane and confirm his observations.